Human alveolar echinococcosis (AE), due to infection with the fox tapeworm Echinococcus multilocularis, though globally rare, is one of the most pathogenic helminthic zoonoses. AE has recently been shown however to be highly endemic in central western China amongst Han farming and Tibetan pastoral communities. Pilot studies indicate that such land-use practices, including deforestation, may increase the risk of human AE by optimizing transmission of the parasite between sylvatic hosts (foxes and rodents/small mammals) and between domestic- sylvatic hosts (dogs and small mammals). The long-term objective of this interdisciplinary project is to understand the ecology of E. multilocularis transmission and of human AE disease in the region and elsewhere. The specific aims are to develop predictive models for relative risk of human disease and of transmission potential in animal cycles for these predominately agricultural or pastoral biotopes. Hypotheses relating to occurrence of optimal habitat patches for hosts within given landscapes (in Gansu), and of seasonal occurrence and spatial distribution of small mammal hosts in semi-nomadic communities (in Sichuan) will be tested using a number of tools and approaches. These include, landscape quantification by remote sensing, rodent/small mammal and fox ecology, host immunoassays for parasite detection or exposure, parasite molecular taxonomy, quantitative transmission dynamics for sylvatic and semi-domestic cycles, and of medical and veterinary epidemiology. Predictive models will be tested in the two regional sites in China.